1. Field of the Invention
The invention relates to a radar apparatus for use in a vehicle.
2. Description of the Related Art
A technology in which a radar apparatus is attached to a vehicle so as to monitor the surroundings of the vehicle, and detects an obstacle or the like is in use. Generally, the radar device of the radar apparatus is installed behind a bumper. For example, Japanese Patent Application Publication No. 11-231041 (JP-A-11-231041) describes a technology in which a radar device is placed behind a bumper, and the bumper is used as a radome. Besides, the radar device is placed on the vehicle so that the beam axis of the radar device faces in the frontal direction of the vehicle, mainly for the purpose of detecting an object present in the frontal direction of the vehicle.
Meanwhile, it is also conceivable to install a radar device so that the device faces obliquely forward of the vehicle, for the purpose of, for example, avoiding a collision at a crossroad, or the like. If the radar device is placed behind the bumper in the case where the radar device is placed obliquely to the frontal direction of the vehicle, the beam axis of the radar device becomes oblique with respect to the bumper. In this case, unlike the case where the beam axis faces in the frontal direction of the vehicle, the beam axis of the radar device is not perpendicular to the bumper, which gives rise to a possibility that the radar device cannot obtain a desired detection performance. It is also conceivable to change the direction of the bumper to an oblique direction so as to agree with the radar device that is disposed obliquely relative to the frontal direction of the vehicle. However, since the direction of the bumper greatly affects the design of the vehicle, it is desirable that the direction of the bumper remain unchanged.